A randomized trial comparing the effects of Volume Guided Ventilation and Synchronised
Intermittent Positive Pressure Ventilation on the cerebral and mesenteric circulation
following surfactant administration

Background: Natural surfactant administration in infants on conventional pressure limited timecycled
ventilation results in a rapid decrease in anterior cerebral artery (ACA) velocit (1). The
mechanism of this change is unclear, but it may be related to rapid improvement in lung
compliance following natural surfactant administration. A volume-guided ventilation modality
on the Draeger Babylog 8000+ ventilator can limit the volume of gas delivered during rapid
changes in lung compliance.

Methods: Babies ventilated for RDS were randomized to receive SIPPV or VG during surfactant
administration after informed written parental consent. Doppler measurements from the
ascending portion of the anterior cerebral artery (ACA) and proximal part of superior mesentric
artery (SMA) were obtained by standard method (2). Blood flow velocity was derived from the
time-averaged mean of the peak velocity envelope averaged over at least 6 cardiac cycles.
Measurements were obtained prior to surfactant administration and for one hour afterwards.
ANOVA was used for statistical analysis.

Results: Gestation, birthweight, baseline arterial CO2 and mean BP were similar in the 2 groups
(Table 1). There was no significant difference in ACA and SMA velocity between the 2 groups.
Babies on SIPPV showed a reduction in ACA blood flow velocity at 1 and 5 minutes after
surfactant administration. ANOVA showed a significant time effect on ACA blood flow
velocity in the SIPPV group but not in the VG group.

Conclusion: Volume guided ventilation may attenuate some of the cerebral circulatory changes
seen after surfactant administration. This warrants further investigation to establish its clinical
relevance.